Automated Demand Response (ADR) is the response of the demand side, e.g. commercial building loads, to the request from the electrical grid to modify (typically to reduce) their electricity consumption. An ADR event may be called for an afternoon period, notified in advance before the start of the event. An event can last for several hours: 2-6 hours, determined by the grid operator. Since lighting is one of the major consuming loads during typical demand response event, it is common to reduce the lighting consumption for ADR purposes, along with other loads (notably the cooling load).
Demand Responsive lighting control, i.e. the lighting control mechanism to reduce lighting power consumption during ADR events, is mandated by the California energy code, Title 24 Part 6, for new buildings in California, as of July 2014.
Very frequently, the Automated Demand Response control will be an additional control to already existing lighting control mechanisms, such as occupancy control, user manual control, schedule-based control and daylight regulation control. As an ADR event may last for several hours, during which daylight condition and space occupancy may have multiple changes, it is required that consistent reduction can be achieved throughout despite all the changes. This means that the ADR control mechanism should not be overridden by other controls, and vice versa. Therefore, ADR control should not issue a dimming command, since (1) dimming command may be overridden by other controls, and (2) without the knowledge of dimming commands issued by other controls, ADR control may set a higher dimming level, which will increase consumption rather than decrease.
A simple ADR control mechanism that circumvents these disadvantages is letting ADR control change the maximum dim level, hence limiting the amount of power light sources can consume. This mechanism will deliver reduction if the prior consumption is higher than the reduced maximum dim level, but will not affect those that are lower.
A closed loop daylight regulation system interacting with an ADR regulation is described by Motegi, et al., Introduction to Commercial Building Control Strategies and Techniques for Demand Response, California Energy Commission, PIER, 2006, LBNL Report Number 59975, p 14-15. The system is configured to scale the dim level upon the start of an ADR event per an ADR signal. But as the target total illumination remains the same, after the dim level scaling, the daylight regulation control loop will attempt to increase the dim level, until the total illumination is back within the required level. This means that the dim level will go back to the approximately same level, or until it reaches the scaled maximum level. This means that if a prior dim level is less than the scaled maximum level, in principle, there will not be any reduction. In other words, any reduction occurrences would be mainly the result of how the prior and post scaling dim levels settled within the dead-band of the daylight regulation control, and will be marginal. If prior dim level is more than the scaled maximum dim level, the reduction is equal to the difference between the prior dim level and the scaled maximum level. Hence, the effect is similar to the limiting effect. The amount of reduction depends on the prior dim level, and it could actually result in no reduction at all.
Patent publication US 2008/088180 discusses a method of determining a setpoint of a load control device for controlling the amount of power delivered to an electrical load located in a space. The method comprises the steps of initially setting the value of the setpoint equal to a desired level; limiting the value of the setpoint to an occupied high-end trim if the space is occupied; limiting the value of the setpoint to a daylighting high-end trim determined by a daylighting procedure; and subsequently reducing the value of the setpoint in response to a load shed parameter. It is noted that scaling the set-point alone may not result in reduction, if the prior measured illumination due to combined daylight and artificial light is still within the dead-band of the new set-point. If any reduction is realized, the reduction will vary depending on the prior measured illumination, the scaling factor, and the width of the dead-band. This will not result in a predictable reduction.